Shipping and ports group P&O has had its £3.9bn ($6.8bn) takeover by Dubai Ports World approved by a High Court judge in London.
Buying P&O would turn DPW into the world's third-biggest port operator
The bid from the United Arab Emirates based firm had faced opposition in the US, where P&O runs ports at key cities including Miami and New York.
P&O's US partner, Eller & Co, had tried to get the takeover blocked on the grounds it would cost jobs.
US politicians had also opposed the deal due to security concerns.
A number of US politicians voiced their concern at such key ports falling into Middle Eastern ownership.
"The objections of Eller do not persuade me that I should not sanction the scheme," said Justice Nicholas Warren.
P&O and Dubai Ports World (DPW) said in a joint statement that they would now continue with the deal under the agreed terms.
Eller, which has also voiced security concerns, said it was "very disappointed" with the decision.
"We remain deeply concerned for the future of our business and the livelihood of thousands of staff and subcontractors," said a spokesman.
"We will continue to fight for our survival."
A lawyer for P&O told the court that Eller's case was "woefully thin", and said the company would seek to recover its court costs from Eller.
DPW has already received regulatory approval in the US for the deal from the federal Committee for Foreign Investment in the United States.
DPW has also volunteered to submit itself to a second 45-day investigation of the deal's potential security risks.
Friend of US
Despite the concern of both Republican and Democrat politicians in the US, President George W Bush has repeatedly insisted the deal would not compromise national security.
"If there was any doubt in my mind or people in my administration's minds that our ports would be less secure or the American people in danger, this deal wouldn't go forward," he said.
London-based P&O operates at 21 ports across the US.
"We consider our company to be a friend of the United States," DPW executive Michael Moore told the BBC earlier this week.
Buying P&O will turn DPW into the world's third-largest port operator.